A revolutionary waterless toilet powered by the sun, developed to help some of the 2.5 billion people lacking safe and sustainable sanitation around the world, will be unveiled in India this month.
Designed and built using a USD 7,77,000 grant from the Bill & Melinda Gates
Foundation, the self-contained, waterless toilet with its innovative technology converts human waste to biochar, a highly porous charcoal.

The toilet has the capability of heating human waste to a high enough temperature to sterilise it and create biochar, a highly porous charcoal, said Karl Linden, project principal investigator and professor at the university of Colorado.

The biochar has a one-two punch in that it can be used to both increase crop yields and sequester carbon dioxide, a greenhouse gas.

The project is part of the Gates Foundation's "Reinvent the Toilet Challenge," an effort to develop a next-generation toilet that can be used to disinfect liquid and solid waste while generating useful end products, both in developing and developed nations, said Linden.

Since the 2012 grant, Linden and his team have received an additional USD 1 million from the Gates Foundation for the project, which includes a team of more than a dozen faculty, research professionals and students, many working full time on the project.

Linden's team is one of 16 around the world funded by the Gates "Reinvent the Toilet Challenge" since 2011.

All have shipped their inventions to Delhi, where they will be on display on March 20-22 for scientists, engineers and dignitaries.

"Biochar is a valuable material," said Linden.

Linden added, "It has good water holding capacity and it can be used in agricultural areas to hold in nutrients and bring more stability to the soils."

"A soil mixture containing 10% biochar can hold up to 50% more water and increase the availability of plant nutrients," he said.

Additionally, the biochar can be burned as charcoal and provides energy comparable to that of commercial charcoal.

While the current toilet has been created to serve four to six people a day, a larger facility that could serve several households simultaneously is under design with the target of meeting a cost level of five cents a day per user set by the Gates Foundation.